Marriage is more beneficial for a woman knocking almost two years off her age (and if she moves up the social ladder she can look four years younger – and the same applies to men).

For men marriage generally only knocks off one year but having one to three children makes a man look a year younger while it makes no difference to a woman.

These benefits disappear in families with four children.

Looking chubbier as you get older helps men look younger as it smooths out the wrinkles. Adding 2 points to your body mass index (bmi) will take off a year whereas a woman would have to add 7 points to her bmi to get the same effect.

An affluent married man with no more than three children will look ten years younger than someone who is homeless, single and has lost weight (2 points off his bmi).

All the factors combined can lead to people in their 40s looking up to seven years younger than their contemporaries.

Public Health scientists at the Danish twin registry led the study published in the journal Age and Ageing.

They asked nurses to guess the ages of almost 2,000 identical and non-identical twins in their seventies. They then looked at environmental factors including marriage, parenthood and social class. Previous studies have shown that non-genetic factors account for 40% of the variation in perceived age.

The effects of heavy smoking are relatively modest. You would have to smoke 20 a day for 20 years to gain extra wrinkles and tobacco smoke only causes half that damage to women’s skin.

However heavy drinking can add a year to both sexes as can diabetes, chronic asthma or the regular use of painkillers.

Excessive exposure to sunlight had no effect on the perception of men’s ages but added over a year to women’s faces by the time they reached seventy.

Depression makes women look a lot older than men. Almost 4 extra years compared with 2.4 for men.

One of the researchers, Dr Kaare Christensen, said “It is a lot more dangerous looking one year older than one year younger”. “If you are not depressed, not lonely, not a smoker, and not too skinny, you are basically doing well”.

Dr Chris Philipson, professor of social gerontology at Keele University says “diet and exercise are crucial factors. You can do an awful lot over the age of 40 to 50 to change the way you experience growing old“.

For years scientists have said that married people are happier, healthier and wealthier than single people.

Well it’s not true!

Single people exercise more, have better health and more friends compared to married people.

Psychologist Bella DePaulo says earlier studies are flawed because they didn’t take into account the consequences of divorce. In most studies people for whom marriage was awful were excluded as divorcees were counted as singletons.

In reality married people are unlikely to see life as a continuous opportunity to learn new things and develop friendships.

They are more likely to be putting up with an unfulfilling job and a dwindling circle of friends a they await their end.

DePaulo says that for many people being single is a positive, rational choice and they are living the dream.

Lifelong singletons also have more fulfilling jobs and are more interested in self-improvement.

according to Janice Turner in the Times. Figures released by the Office of National Statistics show that a third of British households are single person households. Back in 1971 the figure was just 17%.

We haven’t reached the level of Manhattan where half the households are single person but it seems we’re getting there.

Turner points out that in the 1970s it was mainly old people who lived alone. Now, in addition to what she calls late-onset divorces and couples splitting up once the kids have left home, young people are getting married later (although I suspect there might be a dip in these figures reflecting the recession and the fact that many adult children are back at home with parents saving for a deposit for a home).

When I posted on“Living together apart” two years ago it was about the increasing phenomenon of couples, estimated to be a million of them, who chose to keep their own homes even when in a relationship.

Various reasons have been put forward including modern homes being too small for all the accrued possessions and people wanting their own space or style.

Whatever the reason gone are the days when couples would stay together out of habit when the relationship had died.

Sadly women still come off better when they are left on their own, probably because they know how to look after themselves whereas men are less capable in that respect.